Schiff base oligomers

ABSTRACT

Aspects of the present disclosure relate to Schiff base oligomers and uses thereof. In at least one aspect, an oligomer is represented by Formula (IV) wherein each instance of R 9  is independently selected from the group consisting of alkyl, cycloalkyl, aryl, heteroaryl, and ether. Each instance of R 28  and R 29  of Formula (IV) is independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, and aryl. Each instance of R 33  of Formula (IV) is independently selected from the group consisting of alkyl, cycloalkyl, aryl, heterocyclyl, and a bond. Each instance of R 41  of Formula (IV) is independently —NH— or a bond and each instance of R 40  is independently —NH— or —NH—NH—. Each instance of R 42  of Formula (IV) is independently —NH— or a bond and each instance of R 43  is independently —NH— or —NH—NH—.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/985,579, filed Mar. 5, 2020. The above referenced application isincorporated herein by reference in its entirety.

FIELD

Aspects of the present disclosure relate to Schiff base oligomers anduses thereof.

BACKGROUND

Metals, such as steel, aluminum, aluminum alloys, and galvanized metals,used in the manufacture of aircraft, spacecraft, and other machinery canbe susceptible to corrosion. Chromates, such as zinc salts of hexavalentchromium, have been used as corrosion inhibitors in corrosion inhibitingcoatings such as in paints, sealants and wash primers. There is a desireto reduce the amount of chromate used in coatings and otherapplications.

Overall, hex-chrome alternative corrosion inhibitors can havelimitations compared against those containing hexavalent chromium andtheir adhesion may be inadequate to underlying substrates and coatingsdisposed thereon, particularly to meet aerospace performancerequirements.

There is a need for new corrosion inhibitors to provide improvedcoatings to protect metal surfaces against corrosion while using littleor no hexavalent chromium.

SUMMARY

Aspects of the present disclosure relate to Schiff base oligomers anduses thereof.

In at least one aspect, an oligomer is represented by Formula (IV):

wherein:each instance of R⁹ is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heteroaryl, and ether;each instance of R²⁸ and R²⁹ is independently selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, and aryl;each instance of R³³ is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heterocyclyl, and a bond;each instance of R⁴¹ is independently —NH— or a bond and each instanceof R⁴⁰ is independently —NH— or —NH—NH—;each instance of R⁴² is independently —NH— or a bond and each instanceof R⁴³ is independently —NH— or —NH—NH—;each instance of z and t is an integer of 1 to 50;R⁴⁴ is hydroxyl, or hydroxy-substituted alkyl, or is represented by thestructure:

wherein:

R¹ is hydrogen or silyl;

R² and R³ are independently selected from the group consisting ofhydrogen, alkyl, cycloalkyl, and aryl;

R³¹ is selected from the group consisting of alkyl, cycloalkyl, aryl,heterocyclyl, and a bond;

R⁵⁰ is —NH— or a bond and R³² is —NH— or —NH—NH—;

R³⁴ is —NH— or a bond and R³⁵ is —NH— or —NH—NH—; and

x is an integer of 1 to 50; and

R³⁰ is hydrogen, silyl, or is represented by the structure:

where:

R^(9′) selected from the group consisting of alkyl, cycloalkyl, aryl,heteroaryl, and ether; and

R^(44′) is hydroxyl or hydroxy-substituted alkyl.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to Schiff base oligomers anduses thereof. Schiff base oligomers may have one or more silyl groups toprovide for binding to metals to prevent corrosion and enhance adhesionto metals and metal oxides. In general, a Schiff base is a compound withthe general structure R₁R₂C═NR′ where R′≠H.

In some aspects, a Schiff base oligomer includes two or more repeatingunits of a Schiff base monomeric unit, each Schiff base monomeric unithaving at least one thiocarbonyl group. A Schiff base oligomer can havea linking unit linking the two or more repeating units of a Schiff basemonomeric unit. For example, the linking unit can have a hydroxyl group.Alternatively, the linking unit can be a urea-containing unit.

A Schiff base oligomer may be dispersible in a solvent. A Schiff baseoligomer may be in a composition with (e.g., dispersed with or ionicallybonded to) one or more metals. For example, a metal can be a cationicspecies of a transition metal.

In some aspects, a Schiff base oligomer serves as a film-forming coatingin which the Schiff base monomeric unit(s) inhibit metal corrosion. TheSchiff base oligomer provides improved adhesion of the Schiff baseoligomer to the surface of a metal and increased concentration of theinhibitor at the surface, as compared to conventional corrosioninhibitors. A Schiff base oligomer can provide a slow-release orcontrolled release system that can offer long-term corrosion inhibitionby slow dissolution or slow hydrolysis of the polymer or oligomer incomparison to a small molecule Schiff base, such as a small moleculeSchiff base of less than 300 Daltons.

In certain aspects, a Schiff base oligomer has a molecular weight of 300Daltons or more, such as 500 Daltons or more, such as 1,000 Daltons ormore, such as 10,000 Daltons or more, such as 15,000 Daltons or more.

A Schiff base oligomer can interact with a metal (e.g., of a compositionand/or a metal substrate) through the tertiary nitrogen atoms and thethiocarbonyl sulfur atom. By having a large number of groups on the samemolecule capable of interacting (e.g., chelating) with a metal, once aninitial group interacts with, e.g., the metal surface, each subsequentgroup can interact with a lower loss of enthalpy, lowering the barrierto formation and increasing the stability, ultimately improving theadhesion of the Schiff base oligomer as compared to conventionalcorrosion inhibitors. In addition, in examples where a Schiff baseoligomer has a silyl end cap, the silyl group can provide furtheradhesion of the Schiff base oligomer to a substrate via one or moreatoms of the silyl group.

In certain aspects, a Schiff base oligomer has good adhesion to metal(e.g., pure metal, metal alloy, and/or metal oxide) surfaces, andprovides corrosion inhibition by coordination to the surface through theimine, thiocarbonyl, secondary hydroxyl groups, and/or urea-backbonegroups. Additionally, the secondary hydroxyl groups can react with epoxyand urethane primers to provide a tie-layer feature. For example, thehydroxyl groups of a Schiff base oligomer can react with isocyanategroups of urethane primers. The oligomers provide multiple functionalbinding sites, which help provide the required durability and have a lowenough glass transition temperature (Tg) (e.g., about −25° C. or lower)to avoid crystallization.

Adhesion can be determined as described in Rasool et al, J. Inorg.Organomet Polym. 2015, Vol. 15, pp 763-771 which provides detailed IR(Table 2), 1H NMR (section 5.3, and Electronic Spectra (Section 5.4 andTable 3) of free Schiff base complexes and related metal complexes. Thedata confirm the formation of metal bonds to nitrogen and oxygen atomsin the complexes. IR stretching frequencies shift by 8 to 25 cm⁻¹ uponformation of the metal-nitrogen or metal-oxygen bond. The Schiff basesare polymeric species that form complexes to discrete metal atoms.

In certain aspects, a Schiff base oligomer includes polymericthiosemicarbazone monomeric units having imine and thiocarbonyl groupsand one or more optional secondary hydroxyl groups and/or one or moreurea-containing units for providing adhesion to a metal substrate.

A Schiff base oligomer can be reacted with an ether, such aspolyethylene glycol diglycidyl ether, diglycidyl ethers, or othersuitable ethers, to increase the dispersibility of the Schiff baseoligomer. The dispersible Schiff base polymers (e.g., water-soluble,water-dispersible, aqueous-organic solvent blend-soluble,aqueous-organic solvent blend-dispersible, organic solvent-soluble,organic solvent-dispersible) have good adhesion to metal and metal oxidesurfaces, and to provide corrosion inhibition by coordination to thesurface through the imine, thiocarbonyl/carbonyl, and/or hydroxylgroups. Additionally, the hydroxyl groups, such as secondary hydroxylgroups, can react with epoxy and urethane primers to provide a tie-layerfeature. For example, available secondary hydroxyl groups could reactwith isocyanates of polyurethane coating formulations. Formation of acovalent bond may be desirable to bond to primers. The polymers providemultiple functional binding sites, which will help provide the requireddurability and have a low enough Tg (e.g., about −25° C. or lower) toavoid crystallization, e.g., during use in cold environments. A Schiffbase of the present disclosure can provide a corrosion preventioncoating suitable for metals that see the range of temperatureencountered on commercial and defense aircraft where the outside airtemperature at 40,000 feet can be −40° F. or lower.

Methods of Making Schiff Base Oligomers

Methods of making a Schiff base oligomer include reacting a Schiff basemonomer having at least one thiocarbonyl group and at least two terminal—NH₂ groups with a di-carbonyl to form a first reaction product. Forexample, a Schiff base monomer can be a thiocarbazide or athiosemicarbazide. The first reaction product has two terminal —NH₂groups. In some aspects, the Schiff base monomer can be heated, followedby addition of the di-carbonyl, and an acid (such as a strong acid, suchas HCl) to form a reaction mixture. The reaction mixture can be allowedto cool (and optionally cooled below ambient temperature) to form thefirst reaction product.

The first reaction product can be reacted with one or moreepoxy-containing compounds to form a second reaction product having oneor more hydroxyl groups. Alternatively, the first reaction product canbe reacted with one or more isocyanate containing compounds to form asecond reaction product having one or more urea-containing linkages andone or more monomeric units having a thiocarbonyl group. Reaction of thefirst reaction product and epoxy-containing compound (orisocyanate-containing compound) can be performed in the presence of abase (such as NaOH) and/or an acid (such as barbituric acid).

The Schiff base oligomer can include two or more Schiff base monomericunits. The Schiff base monomers used can be thiosemicarbazides,thiocarbazides, or any suitable thiocarbonyl-containing compound havingtwo or more terminal (—NH₂) groups. For example, a Schiff base oligomercan be made by reacting thiocarbazide or thiosemicarbazide and adi-carbonyl comprising two or more carbonyl groups. A carbonylcomprising two or more carbonyl groups are referred to herein as a“di-carbonyl.” The carbonyl groups can be aldehydes, ketones, andcombinations thereof. The carbonyl group of a di-carbonyl can react withthe nitrogen atom of either ends of a thiocarbazide orthiosemicarbazide. Di-carbonyls can link together two or morethiocarbazides or thiosemicarbazides to form the first reaction product.

Alternatively, a Schiff base oligomer can be made by reactingthiocarbazide or thiosemicarbazide and a diisocyanate comprising two ormore isocyanate groups. A carbonyl comprising two or more isocyanategroups are referred to herein as a “diisocyanate.” The carbonyl group ofa diisocyanate can react with the nitrogen atom of either ends of athiocarbazide or thiosemicarbazide. Diisocyanates can link together twoor more thiocarbazides or thiosemicarbazides to form the first reactionproduct.

The terminal amine groups of the first reaction product can react with adi-epoxide to form a Schiff base oligomer. A di-epoxide can provideincreased dispersibility. For example, di-epoxides with hydrophilicgroups can increase the dispersibility of Schiff base oligomer inaqueous solvents or aqueous-organic blend solvents. For example, epoxieswith hydrophobic groups (e.g., organic groups such as alkyl, aryl, etc.)can increase the dispersibility of Schiff base oligomers in organicsolvents. Examples of epoxies that can increase water dispersibilityinclude phenol glycidyl ether; lauryl alcohol glycidyl ether, glycerolpolyglycidyl ether, trimethylolpropane polyglycidyl ether,pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether,polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, ethyleneglycol diglycidyl ether, diethylene glycol diglycidyl ether, diethyleneglycol diglycidyl ether, polyethylene glycol diglycidyl ether. Incertain aspects, the epoxy is a low molecular weight epoxy (e.g., about600 Daltons or less), such as a low molecular weight polyethylene glycoldiglycidyl ether.

Alternatively, the terminal amine groups of the first reaction productcan react with a diisocyanate to form a Schiff base oligomer. Adiisocyanate can provide increased dispersibility. For example,diisocyanates with hydrophilic groups can increase the dispersibility ofSchiff base oligomer in aqueous solvents or aqueous-organic blendsolvents. For example, diisocyanate with hydrophobic groups (e.g.,organic groups such as alkyl, aryl, etc.) can increase thedispersibility of Schiff base oligomers in organic solvents. Examples ofdiisocyanate that can increase water dispersibility includemethylene-bis(phenyl isocyanate) (MDI), toluene diisocyanate (TDI),hexamethylene diisocyanate (HDI), naphthalene diisocyanate (NDI),methylene bis-cyclohexylisocyanate (HMDI)(hydrogenated MDI), andisophorone diisocyanate (IPDI).

In some aspects, a Schiff base oligomer is a silyl-end capped Schiffbase oligomer. A Schiff base oligomer may have one or more terminalamine groups. The one or more terminal amine groups can be reacted witha silyl-containing end cap compound to provide a silyl-end capped Schiffbase oligomer. For example, a silyl-containing end cap can have areactive moiety (e.g., an epoxy group or a leaving group such as ahalogen). In some examples, a silyl-containing end cap is anepoxy-containing silyl-containing end cap. The silyl-end capped Schiffbase oligomer can provide additional adhesion capability to a substrate.

Methods of Disposing Schiff Base Oligomers onto Substrates

In some aspects, a method comprises applying a Schiff base oligomer(e.g., dispersed in a solvent) to a substrate, such as a metalsubstrate. A Schiff base oligomer can be applied over a metal byspraying, brushing, roller coating, or dipping, e.g., for completecoating of a surface. A material that can be applied by a range ofmethods allows for uses of this technology to be scaled up. The aircraftindustry might use spray, whereas an automotive company might use a diptank for auto frames and rail car manufacturers might use roller orbrush methods. The Schiff base oligomer can be dispersible in an aqueoussolvent, an organic solvent, or an aqueous-organic solvent blend.Functional groups of the Schiff base oligomer can be reacted with othercomponents, e.g., to increase its dispersibility. In comparison, smallmolecular Schiff bases are often solid and often can only be applied asa particulate.

In certain aspects, a Schiff base oligomer provides corrosion protectionover a long period of time as determined by pass/fail of a 3000 hourASTM B117 salt fog exposure test. The Schiff base oligomer can form acontinuous film that provides corrosion inhibition for metal surfacesfor a prolonged period of time. The Schiff base oligomer can form acoating to inhibit corrosion of metal surfaces of aerospace vehicles,cars, trucks, trains, boats, ships, buildings, bridges, and other metalcomponents.

Schiff Base Oligomers

In some aspects, a Schiff base oligomer is represented by Formula (I):

where:each instance of R⁴, R⁵, R⁶, R⁷, R⁸, R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ isindependently selected from the group consisting of hydrogen, alkyl,cycloalkyl, alkoxyl, aryloxyl, ether, and heterocyclyl; each instance ofR⁹ is independently selected from the group consisting of alkyl,cycloalkyl, aryl, heterocyclyl, and ether;each instance of R²⁸ and R²⁹ is independently selected from the groupconsisting of hydrogen, alkyl, and aryl;each instance of R³³ is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heterocyclyl, and a bond;each instance of R⁴¹ is independently —NH— or a bond and each instanceof R⁴⁰ is independently —NH— or —NH—NH—;each instance of R⁴² is independently —NH— or a bond and each instanceof R⁴³ is independently —NH— or —NH—NH—;each instance of Q is independently —CH₂— or oxygen;each instance of n, m, z and t is an integer of 1 to 50, such as aninteger independently selected from the group consisting of 1, 2, 3, 4,5, 6, 7, 8, 9, and 10;R⁴⁴ is hydroxyl, hydroxy-substituted alkyl, or is represented by thestructure:

where:

R¹ is hydrogen or silyl;

R² and R³ are independently selected from the group consisting ofhydrogen, alkyl, and aryl;

R³¹ is selected from the group consisting of alkyl, cycloalkyl, aryl,heterocyclyl, and a bond;

R⁵⁰ is —NH— or a bond and R³² is —NH— or —NH—NH—;

R³⁴ is —NH— or a bond and R³⁵ is —NH— or —NH—NH—; and

x is an integer of 1 to 50, such as an integer selected from the groupconsisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10; and

R³⁰ is hydrogen, silyl, or is represented by the structure:

where:

each of R^(4′), R^(5′), R^(6′), R^(7′), R^(8′), R^(10′), R^(11′),R^(12′), R^(13′), and R^(14′) is independently selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, alkoxyl, aryloxyl, ether, andheterocyclyl;

R^(9′) selected from the group consisting of alkyl, cycloalkyl,heterocyclyl, and ether;

R^(44′) is hydroxyl or hydroxy-substituted alkyl;

each instance of Q′ is independently —CH₂— or oxygen; and

each of n′ and m′ is an integer of 1 to 50, such as an integerindependently selected from the group consisting of 1, 2, 3, 4, 5, 6, 7,8, 9, and 10.

In some aspects, each instance of R⁴, R⁵, R⁶, R⁷, R⁸, R¹⁰, R¹¹, R¹²,R¹³, and R¹⁴ (or R^(4′), R^(5′), R^(6′), R^(7′), R^(8′), R^(10′),R^(11′), R^(12′), R^(13′), and R^(14′)) is independently selected fromthe group consisting of hydrogen and C₁-C₅ alkyl. In some aspects, eachinstance of R⁴, R⁵, R⁶, R⁷, R⁸, R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ (or R^(4′),R^(5′), R^(6′), R^(7′), R^(8′), R^(10′), R^(11′), R^(12′), R^(13′), andR^(14′)) is hydrogen. In some aspects, each instance of R²⁸ or R²⁹ (orR² and R³) is independently selected from the group consisting ofhydrogen and C₁-C₅ alkyl. In some aspects, each instance of R²⁸ or R²⁹(or R² and R³) is hydrogen. In some aspects, each instance of Q isoxygen.

In some aspects, if R⁴¹ is —NH—, then R⁴⁰ is —NH—, and/or if R⁴¹ is abond, then R⁴⁰ is —NH—NH—. In some aspects, if R⁴² is —NH—, then R⁴³ is—NH—, and/or if R⁴² is a bond, then R⁴³ is —NH—NH—.

In some aspects, if R⁵⁰ is —NH—, then R³² is —NH—, wherein if R⁵⁰ is abond, then R³² is —NH—NH—. In some aspects, if R³⁴ is —NH—, then R³⁵ is—NH—, wherein if R³⁴ is a bond, then R³⁵ is —NH—NH—.

In some aspects, each instance of R⁹ (or R^(9′)) is independently C₁-C₁₀alkyl or a polyether. For example, R⁹ (or R^(9′)) may be a polyetherselected from polyethylene glycol and polypropylene glycol. Thepolyethylene glycol or polypropylene glycol can have a molecular weightof about 100 g/mol to about 1,000 g/mol, such as about 400 g/mol toabout 700 g/mol.

In some aspects, each instance of R³³ (or R³¹) is a bond. In someaspects, each instance of R³³ (or R³¹) is independently selected fromC₁-C₁₀ alkyl. In some aspects, each instance of R³³ (or R³¹) isindependently selected from a phenyl. For example, a phenyl may berepresented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from hydrogenand C₁-C₁₀ alkyl. In some examples, each of R⁶⁰, R⁶¹, R⁶², and R⁶³ ishydrogen.

In some aspects, R³⁰ and R¹ are hydrogen. In some aspects, one or bothof R³⁰ and R¹ are silyl. For example, a silyl may be a glycidyl ethersilyl. In some aspects, a silyl is represented by the formula:

where R⁴⁵, R⁴⁶, and R⁴⁷ are independently selected from the groupconsisting of hydrogen and C₁-C₂₀alkyl, such as C₁-C₅ alkyl; and R⁴⁸ isselected from the group consisting of (divalent) alkyl, cycloalkyl,ether, and aryl. In some aspects, R⁴⁸ is alkyl or ether. In someaspects, silyl is

In some aspects, a Schiff base oligomer is represented by Formula (II):

where:a wavy line is a line splitting a single bond and indicates a connectionpoint at a second wavy line of the oligomer represented by Formula (II)(In other words, R³⁶ is bonded to the carbon located alpha to R¹⁴);each of R⁴, R⁵, R⁶, R⁷, R⁸, R¹⁰, R¹¹, R¹², R¹³, R¹⁴, R¹⁷, R¹⁸, R¹⁹, R²⁰,R²¹, R²³, R²⁴, R²⁵, R²⁶, and R²⁷ is independently selected from thegroup consisting of alkyl, cycloalkyl, alkoxyl, aryloxyl, heterocyclyl,and ether;each of R⁹ and R²² is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heteroaryl, and ether;each instance of R², R³, R¹⁵, R¹⁶, R²⁸ and R²⁹ is independently selectedfrom the group consisting of hydrogen, alkyl, cycloalkyl, and aryl;each instance of R³¹, R³³, and R⁵¹ is independently selected from thegroup consisting of alkyl, cycloalkyl, aryl, heterocyclyl, and a bond;each instance of R³⁴, R³⁷, R³⁸, R⁴¹, R⁴², and R⁵⁰ is independently —NH—or a bond and each instance of R³², R³⁵, R³⁶, R³⁹, R⁴⁰, and R⁴³ isindependently —NH— or —NH—NH—; each instance of Q is independently —CH₂—or oxygen;each instance of n, m, p, q, x, y, and z is an integer of 1 to 50, suchas an integer independently selected from the group consisting of 1, 2,3, 4, 5, 6, 7, 8, 9, and 10; and each of R¹ and R³⁰ is independentlyselected from the group consisting of hydrogen and silyl.

In some aspects, each of x, y, and z of Formula (II) is the integer 1.

In some aspects, each instance of R⁴, R⁵, R⁶, R⁷, R⁸, R¹⁰, R¹¹, R¹²,R¹³, R¹⁴, R¹⁷, R¹⁸, R¹⁹, R²⁰, R²¹, R²³, R²⁴, R²⁵, R²⁶, and R²⁷ ofFormula (II) is independently selected from the group consisting ofhydrogen and C₁-C₅ alkyl. In some aspects, each instance of R⁴, R⁵, R⁶,R⁷, R⁸, R¹⁰, R¹¹, R¹², R¹³, R¹⁴, R¹⁷, R¹⁸, R¹⁹, R²⁰, R²¹, R²³, R²⁴, R²⁵,R²⁶, and R²⁷ is hydrogen. In some aspects, each instance of R², R³, R¹⁵,R¹⁶, R²⁸ and R²⁹ is independently selected from the group consisting ofhydrogen and C₁-C₅ alkyl. In some aspects, each instance of R², R³, R¹⁵,R¹⁶, R²⁸ and R²⁹ is hydrogen. In some aspects, each instance of Q isoxygen.

In some aspects, if R³⁴, R³⁷, R³⁸, R⁴¹, R⁴², and R⁵⁰ of Formula (II) are—NH—, then, respectively, R³², R³⁵, R³⁶, R³⁹, R⁴⁰, and R⁴³ are —NH—. Insome aspects, if R³⁴, R³⁷, R³⁸, R⁴¹, R⁴², and R⁵⁰ are a bond, then,respectively, R³², R³⁵, R³⁶, R³⁹, R⁴⁰, and R⁴³ are —NH—NH—.

In some aspects, each instance of R⁹ and R²² of Formula (II) isindependently C₁-C₁₀ alkyl or a polyether. For example, R⁹ or R²² may bea polyether selected from polyethylene glycol and polypropylene glycol.The polyethylene glycol or polypropylene glycol can have a molecularweight of about 100 g/mol to about 1,000 g/mol, such as about 400 g/molto about 700 g/mol.

In some aspects, each instance of R³¹, R³³, and R⁵¹ of Formula (II) is abond. In some aspects, each instance of R³¹, R³³, and R⁵¹ isindependently selected from C₁-C₁₀ alkyl. In some aspects, each instanceof each instance of R³¹, R³³, and R⁵¹ is independently selected from aphenyl. For example, a phenyl may be represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from the groupconsisting of hydrogen and C₁-C₁₀ alkyl. In some examples, each of R⁶⁰,R⁶¹, R⁶², and R⁶³ is hydrogen.

In some aspects, R¹ and R³⁰ of Formula (II) are hydrogen. In someaspects, one or both of R¹ and R³⁰ are silyl. For example, a silyl maybe a glycidyl ether silyl. In some aspects, a silyl is represented bythe formula:

where R⁴⁵, R⁴⁶, and R⁴⁷ are independently selected from the groupconsisting of hydrogen and C₁-C₂₀alkyl, such as C₁-C₅ alkyl; and R⁴⁸ isselected from the group consisting of (divalent) alkyl, cycloalkyl,ether, and aryl. In some aspects, R⁴⁸ is alkyl or ether. In someaspects, silyl is

In some aspects, a Schiff base oligomer is represented by Formula (III).

where:a wavy line is a line splitting a single bond shown to indicate aconnection point at a second wavy line of the oligomer represented byFormula (III) (In other words, the NH group next to the wavy line isbonded to the carbon located alpha to R¹⁴);each of R⁴, R⁵, R⁶, R⁷, R⁸, R¹⁰, R¹¹, R¹², R¹³, R¹⁴, R¹⁷, R¹⁸, R¹⁹, R²⁰,R²¹, R²³, R²⁴, R²⁵, R²⁶, and R²⁷ is independently selected from thegroup consisting of hydrogen, alkyl, cycloalkyl, alkoxyl, aryloxyl,heterocyclyl, and ether;each of R⁹ and R²² is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heteroaryl, and ether;each instance of R², R³, R¹⁵, R¹⁶, R²⁸ and R²⁹ is independently selectedfrom the group consisting of hydrogen, alkyl, cycloalkyl, and aryl;each instance of R³¹, R³², and R³³ is independently selected from thegroup consisting of alkyl, cycloalkyl, aryl, heterocyclyl, and a bond;each instance of n, m, p, and q is an integer of 1 to 50, such as aninteger independently selected from the group consisting of 1, 2, 3, 4,5, 6, 7, 8, 9, and 10; and each of R¹ and R³⁰ is independently selectedfrom the group consisting of hydrogen and silyl.

In some aspects, each instance of R⁴, R⁵, R⁶, R⁷, R⁸, R¹⁰, R¹¹, R¹²,R¹³, R¹⁴, R¹⁷, R¹⁸, R¹⁹, R²⁰, R²¹, R²³, R²⁴, R²⁵, R²⁶, and R²⁷ ofFormula (III) is independently selected from the group consisting ofhydrogen and C₁-C₅ alkyl. In some aspects, each instance of R⁴, R⁵, R⁶,R⁷, R⁸, R¹⁰, R¹¹, R¹², R¹³, R¹⁴, R¹⁷, R¹⁸, R¹⁹, R²⁰, R²¹, R²³, R²⁴, R²⁵,R²⁶, and R²⁷ is hydrogen. In some aspects, each instance of R², R³, R¹⁵,R¹⁶, R²⁸ and R²⁹ is independently selected from the group consisting ofhydrogen and C₁-C₅ alkyl. In some aspects, each instance of R², R³, R¹⁵,R¹⁶, R²⁸ and R²⁹ is hydrogen.

In some aspects, each instance of R⁹ and R²² of Formula (III) isindependently C₁-C₁₀ alkyl or a polyether. For example, R⁹ or R²² may bea polyether selected from polyethylene glycol and polypropylene glycol.The polyethylene glycol or polypropylene glycol can have a molecularweight of about 100 g/mol to about 1,000 g/mol, such as about 400 g/molto about 700 g/mol.

In some aspects, each instance of R³¹, R³², and R³³ of Formula (III) isa bond. In some aspects, each instance of R³¹, R³², and R³³ isindependently selected from C₁-C₁₀ alkyl. In some aspects, each instanceof each instance of R³¹, R³², and R³³ is independently selected from aphenyl. For example, a phenyl may be represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from the groupconsisting of hydrogen and C₁-C₁₀ alkyl. In some examples, each of R⁶⁰,R⁶¹, R⁶², and R⁶³ is hydrogen.

In some aspects, R¹ and R³⁰ of Formula (III) are hydrogen. In someaspects, one or both of R¹ and R³⁰ are silyl. For example, a silyl maybe a glycidyl ether silyl. In some aspects, a silyl is represented bythe formula:

where R⁴⁵, R⁴⁶, and R⁴⁷ are independently selected from the groupconsisting of hydrogen and C₁-C₂₀alkyl, such as C₁-C₅ alkyl; and R⁴⁸ isselected from the group consisting of (divalent) alkyl, cycloalkyl,ether, and aryl. In some aspects, R⁴⁸ is alkyl or ether. In someaspects, silyl is

In some aspects, a Schiff base oligomer is represented by Formula (IV):

where:each instance of R⁹ is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heteroaryl, and ether;each instance of R²⁸ and R²⁹ is independently selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, and aryl;each instance of R³³ is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heterocyclyl, and a bond;each instance of R⁴¹ is independently —NH— or a bond and each instanceof R⁴⁰ is independently —NH— or —NH—NH—;each instance of R⁴² is independently —NH— or a bond and each instanceof R⁴³ is independently —NH— or —NH—NH—;each instance of z and t is an integer of 1 to 50, such as an integerindependently selected from the group consisting of 1, 2, 3, 4, 5, 6, 7,8, 9, and 10;R⁴⁴ is hydroxyl or decarboxylated derivative thereof, or is representedby the structure:

where:

R¹ is hydrogen or silyl;

R² and R³ are independently selected from the group consisting ofhydrogen, alkyl, cycloalkyl, and aryl;

R³¹ is selected from the group consisting of alkyl, cycloalkyl, aryl,heterocyclyl, and a bond;

R⁵⁰ is —NH— or a bond and R³² is —NH— or —NH—NH—;

R³⁴ is —NH— or a bond and R³⁵ is —NH— or —NH—NH—; and

x is an integer of 1 to 50, such as an integer selected from the groupconsisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10; and

R³⁰ is hydrogen, silyl, or is represented by the structure:

where:

R^(9′) selected from the group consisting of alkyl, cycloalkyl, aryl,heteroaryl, and ether; and

R^(44′) is hydroxyl or decarboxylated derivative thereof.

In some aspects of Formula (IV), each instance of R²⁸ or R²⁹ (or R² andR³) is independently selected from the group consisting of hydrogen andC₁-C₅ alkyl. In some aspects, each instance of R²⁸ or R²⁹ (or R² and R³)is hydrogen.

In some aspects of Formula (IV), if R⁴¹ is —NH—, then R⁴⁰ is —NH—,and/or if R⁴¹ is a bond, then R⁴⁰ is —NH—NH—. In some aspects, if R⁴² is—NH—, then R⁴³ is —NH—, and/or if R⁴² is a bond, then R⁴³ is —NH—NH—.

In some aspects of Formula (IV), if R⁵⁰ is —NH—, then R³² is —NH—,wherein if R⁵⁰ is a bond, then R³² is —NH—NH—. In some aspects, if R³⁴is —NH—, then R³⁵ is —NH—, wherein if R³⁴ is a bond, then R³⁵ is—NH—NH—.

In some aspects of Formula (IV), each instance of R⁹ (or R^(9′)) isindependently C₁-C₁₀ alkyl or an aryl. R⁹ (or R^(9′)) may be a C₁-C₁₀cycloalkyl that is cyclohexyl. R⁹ (or R^(9′)) may be an aryl that isphenyl. For example, a phenyl may be represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from hydrogenand C₁-C₁₀ alkyl. In some examples, each of R⁶⁰, R⁶¹, R⁶², and R⁶³ ishydrogen.

In some aspects of Formula (IV), each instance of R³³ (or R³¹) is abond. In some aspects, each instance of R³³ (or R³¹) is independentlyselected from C₁-C₁₀ alkyl. In some aspects, each instance of R³³ (orR³¹) is independently selected from a phenyl. For example, a phenyl maybe represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from hydrogenand C₁-C₁₀ alkyl. In some examples, each of R⁶⁰, R⁶¹, R⁶², and R⁶³ ishydrogen.

In some aspects of Formula (IV), R³⁰ and R¹ are hydrogen. In someaspects, one or both of R³⁰ and R¹ are silyl. For example, a silyl maybe a glycidyl ether silyl. In some aspects, a silyl is represented bythe formula:

where R⁴⁵, R⁴⁶, and R⁴⁷ are independently selected from the groupconsisting of hydrogen and C₁-C₂₀alkyl, such as C₁-C₅ alkyl; and R⁴⁸ isselected from the group consisting of (divalent) alkyl, cycloalkyl,ether, and aryl. In some aspects, R⁴⁸ is alkyl or ether. In someaspects, silyl is

In some aspects, a Schiff base oligomer is represented by Formula (V):

where:a wavy line is a line splitting a single bond shown to indicate aconnection point at a second wavy line of the oligomer represented byFormula (V) (In other words, R³⁶ is bonded to the carbon located alphato R¹⁴);each instance of R², R³, R¹⁵, R¹⁶, R²⁸ and R²⁹ is independently selectedfrom the group consisting of hydrogen, alkyl, cycloalkyl, and aryl;each of R⁹ and R²² is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heteroaryl, and ether;each instance of R³¹, R³³, and R⁵¹ is independently selected from thegroup consisting of alkyl, cycloalkyl, aryl, heterocyclyl, and a bond;each instance of R³⁴, R³⁷, R³⁸, R⁴¹, R⁴², and R⁵⁰ is independently —NH—or a bond and each instance of R³², R³⁵, R³⁶, R³⁹, R⁴⁰, and R⁴³ isindependently —NH— or —NH—NH—; each instance of x, y, and z is aninteger of 1 to 50, such as an integer independently selected from thegroup consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10; andeach of R¹ and R³⁰ is independently selected from the group consistingof hydrogen and silyl.

In some aspects, each of x, y, and z of Formula (V) is the integer 1.

In some aspects of Formula (V), each instance of R², R³, R¹⁵, R¹⁶, R²⁸and R²⁹ is independently selected from the group consisting of hydrogenand C₁-C₅ alkyl. In some aspects, each instance of R², R³, R¹⁵, R¹⁶, R²⁸and R²⁹ is hydrogen.

In some aspects, if R³⁴, R³⁷, R³⁸, R⁴¹, R⁴², and R⁵⁰ of Formula (V) are—NH—, then, respectively, R³², R³⁵, R³⁶, R³⁹, R⁴⁰, and R⁴³ are —NH—. Insome aspects, if R³⁴, R³⁷, R³⁸, R⁴¹, R⁴², and R⁵⁰ are a bond, then,respectively, R³², R³⁵, R³⁶, R³⁹, R⁴⁰, and R⁴³ are —NH—NH—.

In some aspects, each instance of R⁹ and R²² of Formula (V) isindependently C₁-C₁₀ alkyl or an aryl. R⁹ and R²² may be a C₁-C₁₀cycloalkyl that is cyclohexyl. R⁹ and R²² may be an aryl that is phenyl.For example, a phenyl may be represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from hydrogenand C₁-C₁₀ alkyl. In some examples, each of R⁶⁰, R⁶¹, R⁶², and R⁶³ ishydrogen.

In some aspects, each instance of R³¹, R³³, and R⁵¹ of Formula (II) is abond. In some aspects, each instance of R³¹, R³³, and R⁵¹ isindependently selected from C₁-C₁₀ alkyl. In some aspects, each instanceof each instance of R³¹, R³³, and R⁵¹ is independently selected from aphenyl. For example, a phenyl may be represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from the groupconsisting of hydrogen and C₁-C₁₀ alkyl. In some examples, each of R⁶⁰,R⁶¹, R⁶², and R⁶³ is hydrogen.

In some aspects, R¹ and R³⁰ of Formula (V) are hydrogen. In someaspects, one or both of R¹ and R³⁰ are silyl. For example, a silyl maybe a glycidyl ether silyl. In some aspects, a silyl is represented bythe formula:

where R⁴⁵, R⁴⁶, and R⁴⁷ are independently selected from the groupconsisting of hydrogen and C₁-C₂₀alkyl, such as C₁-C₅ alkyl; and R⁴⁸ isselected from the group consisting of (divalent) alkyl, cycloalkyl,ether, and aryl. In some aspects, R⁴⁸ is alkyl or ether. In someaspects, silyl is

In some aspects, a Schiff base oligomer is represented by Formula (VI):

where:a wavy line is a line splitting a single bond shown to indicate aconnection point at a second wavy line of the oligomer represented byFormula (VI) (In other words, NH next to the wavy line is bonded to thecarbon located alpha to R¹⁴);each of R⁹ and R²² is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heteroaryl, and ether;each of R², R³, R¹⁵, R¹⁶, R²⁸ and R²⁹ is independently selected from thegroup consisting of hydrogen, alkyl, cycloalkyl, and aryl;each of R³¹, R³², and R³³ is independently selected from the groupconsisting of alkyl, cycloalkyl, aryl, heterocyclyl, and a bond; andeach of R¹ and R³⁰ is independently selected from the group consistingof hydrogen and silyl.

In some aspects of Formula (VI), each of R², R³, R¹⁵, R¹⁶, R²⁸ and R²⁹is independently selected from the group consisting of hydrogen andC₁-C₅ alkyl. In some aspects, each of R², R³, R¹⁵, R¹⁶, R²⁸ and R²⁹ ishydrogen.

In some aspects, each instance of R⁹ and R²² of Formula (VI) isindependently C₁-C₁₀ alkyl or an aryl. R⁹ and R²² may be a C₁-C₁₀cycloalkyl that is cyclohexyl. R⁹ and R²² may be an aryl that is phenyl.For example, a phenyl may be represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from hydrogenand C₁-C₁₀ alkyl. In some examples, each of R⁶⁰, R⁶¹, R⁶², and R⁶³ ishydrogen.

In some aspects, each instance of R³¹, R³², and R³³ of Formula (VI) is abond. In some aspects, each instance of R³¹, R³², and R³³ isindependently selected from C₁-C₁₀ alkyl. In some aspects, each instanceof each instance of R³¹, R³², and R³³ is independently selected from aphenyl. For example, a phenyl may be represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from the groupconsisting of hydrogen and C₁-C₁₀ alkyl. In some examples, each of R⁶⁰,R⁶¹, R⁶², and R⁶³ is hydrogen.

In some aspects, R¹ and R³⁰ of Formula (VI) are hydrogen. In someaspects, one or both of R¹ and R³⁰ are silyl. For example, a silyl maybe a glycidyl ether silyl. In some aspects, a silyl is represented bythe formula:

where R⁴⁵, R⁴⁶, and R⁴⁷ are independently selected from the groupconsisting of hydrogen and C₁-C₂₀alkyl, such as C₁-C₅ alkyl; and R⁴⁸ isselected from the group consisting of (divalent) alkyl, cycloalkyl,ether, and aryl. In some aspects, R⁴⁸ is alkyl or ether. In someaspects, silyl is

Metals

A Schiff base oligomer may be dispersible in a solvent. A Schiff baseoligomer may be in a composition with (e.g., dispersed with or ionicallybonded to) one or more metals. For example, a metal can be a cationicspecies of a transition metal.

Metals can be in the form of a cation or a metal salt. For example, ametal may be selected from alkali earth metals, transition metals andrare earth metal salts, for example a group consisting of Zn, La, Pr,Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ce, Co, Y, Bi, Cd, Pb, Ag,Sb, Sn, Cu, Fe, Ni, Li, Ca, Sr, Mg, Zr, Nd, Ba, Sc, and any combinationsthereof. For example, a metal may be selected from a group consisting ofZn, La, Pr, Ce, Co, Y, Ca, Sr, Ba, Sc, and Zr. The metals may beselected from at least one of Zn, Pr and Ce. The metal may be Zn. Themetal may be Ce. The metal may be Pr. Some examples of salts that may beused are nitrate salts, chloride salts, acetate salts, or anycombinations thereof.

It will be appreciated that the metals may have any suitable oxidationstate. For example, the typical oxidation state for Zn is +2. Thetypical oxidation states for Pr are +2, +3 and/or +4. The typicaloxidation states for Ce are +2, +3 and +4. It will be appreciated thatvarious combinations and groups of the above mentioned metal salts, maybe used in the compositions of the present disclosure.

Substrates for Corrosion Protection

Substrates that may be protected from corrosion by a Schiff baseoligomer or composition thereof may be any suitable substrate, such as ametal substrate or plastic substrate. The metal substrate can includeany substrate material having at least a portion of its surface beingmetallic, for example a portion of its external surface being metallic.The metal substrate may comprise any metal requiring protection fromcorrosion. The metal substrate may include a metal or alloy selectedfrom aluminum, for example aluminum alloys. The metal substrate may bean aluminum alloy, for example alloys of aluminum with one or moremetals selected from the group consisting of copper, magnesium,manganese, silicon, tin, zinc, and combinations thereof. An aluminumalloy may be an alloy comprising copper. The metal substrate may be acopper-containing alloy, such as copper-containing aluminum alloy. Theamount of copper in the alloy may be about 1 wt % to about 20 wt %,about 1 wt % to about 18 wt %, about 1 wt % to about 10 wt %, or about 1wt % to about 6 wt %. The aluminum alloy may be an aerospace alloy, forexample AA2XXX and AA7XXX type. For example the aluminum alloy may beAA2024 and AA7075 type. The aluminum alloy may be an automotive alloy,for example AA6XXX type. The aluminum alloy may be a marine alloy, forexample AA5XXX type.

Compositions

The present disclosure also relates to compositions (e.g., forinhibiting corrosion) including (a) a Schiff base oligomer and (b) ametal (e.g., metal salt) selected from a rare earth metal, an alkaliearth metal, a transition metal, or combinations thereof. The Schiffbase oligomer may interact with (e.g., chelate) to the metal. If asolvent (such as water) is included in a composition of the presentdisclosure, the Schiff base oligomer can be dissociated from (e.g.,reversibly coordinated to and from) the metal. In aspects where acomposition is substantially free of a solvent, the Schiff base oligomerand the metal (e.g., metal salt) can be in the form of a coordinationoligomer (e.g., a compound having ionic bonds between the Schiff baseoligomer and the metal), but such coordination oligomers are stillconsidered a composition for purposes of the present disclosure.

For example, a composition may include (a) at least one a Schiff baseoligomer and (b) at least one metal (e.g., metal salt), wherein themetal is selected from the group consisting of Zn, La, Pr, Ce, Nd, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Co, Y, Ca, Sr, Ba, Sc, and Zr. Forexample, the at least one metal may be any one of Zn, Ce, Pr, orcombinations thereof.

The composition may comprise (a) at least one a Schiff base oligomer and(b) at least one metal (e.g., metal salt), wherein the metal is selectedfrom the group consisting of Zn, Pr, Ce, and combinations thereof.

Compositions of the present disclosure may further include a solvent toprovide solubility/dispersibility of the Schiff base oligomer. Solventsmay be water, a glycol, or a ketone. Glycols can include glycolacetates, such as glycol ether acetates. Ketones can include acetone orpentanones. In some aspects, a solvent is 1-methoxy-2-propanol acetate,4-methyl-2-pentanone, or combinations thereof. Schiff base oligomers ofthe present disclosure are very polar. Accordingly, solvents with highdipole features are suitable solvents. A few examples of solvents withmodest evaporation rates can be used. For example, a commercialformulation may include a plurality of solvents, e.g., four or fivesolvents, with differing evaporation to allow for coalescence, drying,and consolidation. Solvents that evaporate too fast such as MEK oracetone might not be desired due to lack of time for wetting of thesurface, coalescence, and avoiding blush (moisture condensation).

The concentration of the Schiff base oligomer may be about 0.001 wt % toabout 20 wt %, such as about 0.1 wt % to about 10 wt %, such as about 1wt % to about 5 wt %, alternatively about 5 wt % to about 10 wt %, whichcan provide solubility/dispersibility of the Schiff base oligomer.

In some aspects, the molar ratio of metal(s) (e.g., metal salt(s):Schiffbase oligomer(s) in a composition is provided with an excess of themetal (e.g., metal salt) in comparison to the Schiff base oligomer, dueto the presence of multiple moieties of the Schiff base oligomer thatare capable of interacting with a metal. For example, the molar ratio ofmetal salt:Schiff base oligomer in the composition may be greater thanabout 1:1, greater than about 1.1:1, greater than about 1.2:1, greaterthan about 1.3:1, greater than about 1.4:1, greater than about 1.5:1,greater than about 1.6:1, greater than about 1.7:1, greater than about1.8:1, greater than about 1.9:1, greater than about 2:1, greater thanabout 3:1, greater than about 4:1, greater than about 5:1, greater thanabout 6:1, greater than about 7:1, greater than about 8:1, greater thanabout 9:1, or greater than about 10:1. The ratio of metal salt:Schiffbase oligomer in the composition may be less than about 45:1, less thanabout 40:1, less than about 35:1, less than about 30:1, less than about25:1, less than about 20:1, less than about 15:1, or less than about10:1. The ratio of metal:corrosion inhibiting agent in the compositionmay be greater than about 1:1 to about 45:1, about 1.5:1 to about 40:1,about 2:1 to about 35:1, about 2.5:1 to about 30:1, about 3:1 to about25:1, about 3.5:1 to about 20:1, about 4:1 to about 15:1, or about 5:1to about 10:1. For example, the ratio of metal:corrosion inhibitingagent in the composition may be about 1.1:1 to about 45:1, about 1.2:1to about 40:1, about 1.3:1 to about 35:1, about 1.4:1 to about 30:1,about 1.5:1 to about 25:1, about 1.6:1 to about 20:1, about 1.7:1 toabout 15:1, about 1.8:1 to about 10:1, about 1.9:1 to about 9:1, orabout 2:1 to about 8:1.

The corrosion inhibitor compositions are suitable for use andapplication to various substrates, such as metal substrates, and forexample can be provided as coating compositions. The compositions mayinclude one or more other additives or corrosion inhibiting agentssuitable for use with a substrate of interest.

After depositing a composition onto a substrate, the solvent (if used)can be partially, substantially, or completely removed by any suitablecuring process. For example, a coating composition can be applied to asubstrate, in either a wet or “not fully cured” condition that dries orcures over time, that is, solvent evaporates. The coatings can dry orcure either at ambient temperature or by accelerated means, for examplean ultraviolet light cured system to form a film or “cured” paint. Thecoatings can also be applied in a semi or fully cured state, such as anadhesive.

The composition can be a coating composition comprising a film-formingorganic polymer. The coating composition may be a paint composition. Thecoating composition may comprise one or more resins, for example epoxybased resins. The coating composition may be a paint composition, forexample an epoxy resin based paint composition.

The coating composition may be a powder coating composition, for examplea powder coating composition suitable for use in powder coating ofvarious metal substrates including aluminum alloys as described hereinor steels.

Compositions of the present disclosure can include one or moreadditives, such as pigments, fillers and extenders. Examples of suitableadditives with which the corrosion inhibitors described herein can becombined include, for example, binders, solvents, pigments (includingsoluble or non-soluble extenders, fillers, corrosion-inhibitingpigments, and the like), additives (e.g., curing agents, surfactants,dyes, amino acids and the like), and so forth. Note that some additivescan also properly be considered a pigment and vice versa (e.g., mattingagents). More specifically, these “additives” include, but are notlimited to, glycine, arginine, methionine, and derivatives of aminoacids, such as methionine sulfoxide, methyl sulfoxide, andiodides/iodates, gelatin and gelatin derivatives, such as animal andfish gelatins, linear and cyclic dextrins, including alpha and betacyclodextrin, triflic acid, triflates, acetates, talc, kaolin,organic-based ionic exchange resins, such as organic-based cationic andanionic exchange resins, organic-based ionic exchange resins that havebeen pre-exchanged or reacted with salts, oxides, and/or mixed oxides ofrare earth material, and/or metal sulfates, such as sulfates of rareearth materials, magnesium sulfate, calcium sulfate (anhydrous andhydrated forms), strontium sulfate, barium sulfate, and the like, andcombinations thereof.

Compositions may also include other additives such as rheologymodifiers, fillers, tougheners, thermal or UV stabilizers, fireretardants, lubricants, surface active agents. The additive(s) areusually present in an amount of less than about 10% based on the totalweight of the composition after curing. Examples include:

(a) rheology modifiers such as hydroxypropyl methyl cellulose (e.g.Methocell 311, Dow), modified urea (e.g. Byk 411, 410) andpolyhydroxycarboxylic acid amides (e.g. Byk 405);

(b) film formers such as esters of dicarboxylic acid (e.g. Lusolvan FBH,BASF) and glycol ethers (e.g. Dowanol, Dow);

(c) wetting agents such as fluorochemical surfactants (e.g. 3M Fluorad)and polyether modified poly-dimethyl-siloxane (e.g. Byk 307, 333);

(d) surfactants such as fatty acid derivatives (e.g. Bermadol SPS 2543,Akzo) and quaternary ammonium salts;

(e) dispersants such as non-ionic surfactants based on primary alcohols(e.g. Merpol 4481, Dupont) and alkylphenol-formaldehyde-bisulfidecondensates (e.g. Clariants 1494);

(f) anti foaming agents;

(g) anti corrosion reagents such as phosphate esters (e.g. ADD APT,Anticor C6), alkylammonium salt of (2-benzothiazolythio) succinic acid(e.g. Irgacor 153 CIBA) and triazine dithiols;

(h) stabilizers such as benzimidazole derivatives (e.g. Bayer, PreventolBCM, biocidal film protection);

(i) leveling agents such as fluorocarbon-modified polymers (e.g. EFKA3777);

(j) pigments or dyes such as fluorescents (Royale Pigment andchemicals);

(k) organic and inorganic dyes such as fluoroscein; and

(l) Lewis acids such as lithium chloride, zinc chloride, strontiumchloride, calcium chloride and aluminium chloride.

(m) Suitable flame retardants which retard flame propagation, heatrelease and/or smoke generation which may optionally include any of thefollowing (or combinations thereof):

-   -   Phosphorus derivatives such as molecules containing phosphate,        polyphosphate, phosphites, phosphazine and phosphine functional        groups, for example, melamine phosphate, dimelamine phosphate,        melamine polyphosphate, ammonia phosphate, ammonia        polyphosphate, pentaerythritol phosphate, melamine phosphite and        triphenyl phosphine.    -   Nitrogen containing derivatives such as melamine, melamine        cyanurate, melamine phthalate, melamine phthalimide, melam        cyanurate, melem cyanurate, melon cyanurate, hexamethylene        tetraamine, imidazole, adenine, guanine, cytosine and thymine.    -   Molecules containing borate functional groups such as ammonia        borate and zinc borate.    -   Molecules containing two or more alcohol groups such as        pentaerythritol, polyethylene alcohol, polyglycols and        carbohydrates, for example, glucose, sucrose and starch.    -   Molecules which endothermically release non-combustible        decomposition gases, such as, metal hydroxides, for example,        magnesium hydroxide and aluminum hydroxide.    -   Expandable graphite.        Aspects

The present disclosure provides, among others, the following aspects,each of which may be considered as optionally including any alternateaspects.

Clause 1. An oligomer represented by Formula (IV):

wherein:each instance of R⁹ is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heteroaryl, and ether;each instance of R²⁸ and R²⁹ is independently selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, and aryl;each instance of R³³ is independently selected from the group consistingof alkyl, cycloalkyl, aryl, heterocyclyl, and a bond;each instance of R⁴¹ is independently —NH— or a bond and each instanceof R⁴⁰ is independently —NH— or —NH—NH—;each instance of R⁴² is independently —NH— or a bond and each instanceof R⁴³ is independently —NH— or —NH—NH—;each instance of z and t is an integer of 1 to 50, such as an integerindependently selected from the group consisting of 1, 2, 3, 4, 5, 6, 7,8, 9, and 10;R⁴⁴ is hydroxyl or decarboxylated derivative thereof, or is representedby the structure:

wherein:

R¹ is hydrogen or silyl;

R² and R³ are independently selected from the group consisting ofhydrogen, alkyl, cycloalkyl, and aryl;

R³¹ is selected from the group consisting of alkyl, cycloalkyl, aryl,heterocyclyl, and a bond;

R⁵⁰ is —NH— or a bond and R³² is —NH— or —NH—NH—;

R³⁴ is —NH— or a bond and R³⁵ is —NH— or —NH—NH—; and

x is an integer of 1 to 50, such as an integer selected from the groupconsisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10; and

R³⁰ is hydrogen, silyl, or is represented by the structure:

where:

R^(9′) selected from the group consisting of alkyl, cycloalkyl, aryl,heteroaryl, and ether; and

R^(44′) is hydroxyl or decarboxylated derivative thereof.

Clause 2. The oligomer of Clause 1, wherein each instance of R²⁸ or R²⁹is independently selected from the group consisting of hydrogen andC₁-C₅ alkyl.

Clause 3. The oligomer of Clause 1 or 2, wherein each instance of R²⁸ orR²⁹ is hydrogen.

Clause 4. The oligomer of any of Clauses 1 to 3, wherein:

if R⁴¹ is —NH—, then R⁴⁰ is —NH—, and if R⁴¹ is a bond, then R⁴⁰ is—NH—NH—; and

if R⁴² is —NH—, then R⁴³ is —NH—, and if R⁴² is a bond, then R⁴³ is—NH—NH—.

Clause 5. The oligomer of any of Clauses 1 to 4, wherein each instanceof R⁹ is independently C₁-C₁₀ alkyl or an aryl.

Clause 6. The oligomer of any of Clauses 1 to 5, wherein each instanceof R⁹ is independently a phenyl represented by the formula:

wherein R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from the groupconsisting of hydrogen and C₁-C₁₀ alkyl.Clause 7. The oligomer of any of Clauses 1 to 6, wherein each of R⁶⁰,R⁶¹, R⁶², and R⁶³ is hydrogen.Clause 8. The oligomer of any of Clauses 1 to 7, wherein each instanceof R⁹ is cycloalkyl.Clause 9. The oligomer of any of Clauses 1 to 8, wherein each instanceof R³³ is a bond.Clause 10. The oligomer of any of Clauses 1 to 9, wherein each instanceof R³³ is independently selected from C₁-C₁₀ alkyl.Clause 11. The oligomer of any of Clauses 1 to 10, wherein each instanceof R³³ is independently selected from a phenyl represented by theformula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from hydrogenand C₁-C₁₀ alkyl.Clause 12. The oligomer of any of Clauses 1 to 11, wherein each of R⁶⁰,R⁶¹, R⁶², and R⁶³ is hydrogen.Clause 13. The oligomer of any of Clauses 1 to 12, wherein R³⁰ ishydrogen.Clause 14. The oligomer of any of Clauses 1 to 13, wherein R⁴⁴ ishydroxyl.Clause 15. The oligomer of any of Clauses 1 to 14, wherein R³⁰ is silyl.Clause 16. The oligomer of any of Clauses 1 to 15, wherein the silyl isa glycidyl ether silyl.Clause 17. The oligomer of any of Clauses 1 to 16, wherein the silyl isrepresented by the formula:

wherein each of R⁴⁵, R⁴⁶, and R⁴⁷ is independently selected from thegroup consisting of hydrogen and C₁-C₂₀ alkyl; and R⁴⁸ is selected fromthe group consisting of alkyl, cycloalkyl, ether, and aryl.Clause 18. The oligomer of any of Clauses 1 to 17, wherein each of R⁴⁵,R⁴⁶, and R⁴⁷ is hydrogen.Clause 19. The oligomer of any of Clauses 1 to 18, wherein each of R⁴⁵,R⁴⁶, and R⁴⁷ is C₁-C₅ alkyl.Clause 20. The oligomer of any of Clauses 1 to 19, wherein each of R⁴⁵,R⁴⁶, and R⁴⁷ is ethyl.Clause 21. The oligomer of any of Clauses 1 to 20, wherein R⁴⁸ is ether.Clause 22. The oligomer of any of Clauses 1 to 21, wherein R⁴⁸ is ether.Clause 23. The oligomer of any of Clauses 1 to 22, wherein the silyl isselected from the group consisting of:

EXAMPLES Example 1

Synthesis of bis-thiosemicarbazones the di-carbonyl compounds wasperformed, followed by formation of oligomers with polyethylene glycoldiglycidyl ether or similar diglycidyl ethers. Water-soluble diglycidylethers of polyethylene glycol are commercially available in 20 kgquantities from Nagase America LLC (Nagase, 2020a, 2020b) with 4, 9, 13or 22 EO (ethylene oxide) repeat units on average which equates tomolecular weights of about 300, 480, 640, and 1000, respectively.

Example 2

Simple dialdehydes such as methyl glyoxal or isophthalaldehyde reactwith two molecules of thiosemicarbazide to give thebis-thiosemicarbazone by refluxing in ethanol. This has the ability toboth bond to metal surfaces through the thiocarbonyls and tertiarynitrogen atoms of the Schiff base, and form a polymer through thethiocarbamide groups by reacting with another carbonyl group or areactive chain extending species such as diglycidyl ether. The use oflow-cost diketones was also performed in which 2,4-pentanedione(acetylacetone) or 2,5-hexanedione (acetonylacetone) could react in thesame manner to give a bis-thiosemicarbazone with a larger distancebetween the bonding sites.

Synthesis of Monomeric Schiff Base

Thiosemicarbazide (0.01 mol, 0.91 g) was dissolved in ethanol (50 cm³)in 250 cm³ three necked round bottom flask and was attached to icecooled reflux condenser fitted over the magnetic stirrer. To thissolution, salicylaldehyde (0.02 mol, 2.44 cm³) in ethanol (20 cm³) wasadded drop wise. The reaction mixture was acidified with concentratedHCl, and refluxed with constant stirring at room temperature for 2 hrs.The reaction mixture was allowed to stand for 40 min. Light yellowprecipitate was obtained, which was filtered and purified by washingrepeatedly with distilled water and diethyl ether. It was dried at 40°C. for 8 h to give monomeric Schiff base, N,N′-bis (Salicylidene)thiosemicarbazide Schiff base, yield 72%.

Synthesis of Schiff Base Oligomer (STFB)

Schiff base oligomer was synthesized by adding formaldehyde (0.02 mol,1.5 cm³) into monomeric Schiff base (0.01 mol, 2.99 gm) in molar ratioof (2:1) in 250 cm³ three necked round bottom flask equipped withthermometer, condenser and magnetic stirrer in 50 cm³ DMF. 0.5 cm³ of40% aq. NaOH was added in this reaction mixture. The temperature wasmaintained up to 70±5° C. for 1 hr with continuous stirring. Theprogress of reaction was monitored by TLC (thin layer chromatography).To this mixture, barbituric acid (0.01 mol, 1.28 gm) in 20 cm³ DMF wasadded and stirred again for about 2 & ½ h up to 100° C. until it gavereddish-yellow sticky compound. It was then precipitated in distilledwater and washed several times with acetone and diethyl ether. Afterdrying it in oven for 5-7 hrs at 40° C., Schiff base oligomer STFB wasobtained 70% yield.

Synthesis of Coordination Oligomers

Coordination oligomers of [Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)]were prepared by using equimolar ratio (1:1) of Schiff base ligand andmetal(II) acetates. The typical procedure for the preparation of metalpolychelate of manganese(II) was as follows: The Schiff base oligomer(0.01 mol) was dissolved in (20 cm³) DMF and heated at 60° C. in athree-necked round bottom flask fitted to an ice-cooled condenser.Solution of manganese (II) acetate tetrahydrate Mn(CH₃COO)₂.4H₂O (0.01mol, 2.45 gm) was added in 15 cm³ DMF with constant stirring to the hotand clear solution of Schiff base and refluxed for 7 hrs. Stirring wascontinued until complete dissolution and distinct color change wasachieved. Finally, a brown colored viscous solution was obtained. It wasthen precipitated, filtered and washed several times with distilledwater and diethyl ether, which gave a brown precipitate. It was thenoven dried at 45° C. for 5-6 hrs to obtain the polychelate of manganese[STFB-Mn(II)], 81% yield.

Reaction 1—Schiff Base Reaction Proof of Concept

Using ethanol as the solvent and concentrated HCl as the reactioncatalyst, both ends of thiosemicarbazide will react with an aldehyde,such as salicylaldehyde as shown below, in 72% isolated yield.

Reaction 2

Making an oligomeric species using about 1.8 equivalents of dialdehyde(or other dicarbonyl such as a keto-aldehyde or diketone) and 1equivalent of thiosemicarbazide as shown below.

Formation of Bis-Thiosemicarbazone of Terephthalaldehyde (1)

A 250 mL three-necked round-bottom flask was charged with a solution ofthiosemicarbazide (9.11 g, 0.100 mole) dissolved in 100 mL of ethanol. APTFE stirring bar was added, and the flask is placed in soft heatingmantle on a magnetic stir plate. The center neck was fitted with areflux condenser. One side-neck was fitted with an addition funnelcharged with a solution of terephthalaldehyde (6.57 g, 0.049 mol) in 50mL of ethanol. The other side neck was fitted with a second additionfunnel charged with a solution of 1 mL of 12 N HCl (concentrated HCl) in20 mL of ethanol.

The solution of terephthalaldehyde was slowly added to the flask withstirring at room temperature over a period of 30 minutes followed by thesolution of HCl. After the acid was added, the heating mantle was turnedon, and the mixture was refluxed for two to three hours. The heat wasturned off, and the mixture was allowed to cool slowly back to roomtemperature. The product precipitated as a yellow solid and collected byfiltration on a Buchner funnel. The product was washed with D.I. water(3×50 mL) and ethyl ether (1×50 mL) and dried in oven at 100 Fovernight. C₁₀H₁₂N₆S₂: mol. wt. 280.41. Yield=13.74 of product.By-products are 0.18 g of excess thiosemicarbazide and 1.76 g of water.

Reaction of (1) with Diglycidyl Ether or Diisocyanates

A solution of 5 grams of the polymer made in the previous section and0.05 gram of the appropriate catalyst was dissolved in 25 mL of solvent.This solution was charged to a 100 mL three-necked round bottom flaskcontaining a PTFE stir bar and fitted with a reflux condenser, additionfunnel, and thermocouple. The flask was placed in a water bath, andplaced on a magnetic heated stirring plate. The addition funnel wascharged with a solution of 0.9 equivalents of the desired chain extender(below) dissolved in 25 mL of the same solvent. This was added dropwiseto the flask with stirring over a period of 30 minutes, and thetemperature was monitored. The temperature should rise as the twocomponents combine. The temperature should be kept below 100° C. byappropriate means such as adding ice to the water bath.

After one hour, all of the reactive chain extender should be consumed.Residual epoxy content can be determined by a titration (ASTM D1652),and residual isocyanate can be determined by titration (Dow, 2000).

TABLE 1 Mol. Material Wt. Eq. Wt. CASRN Reactive chain extenders HDI 16884   822-06-0 Desmodur N (Covestro) H12MDI 262 131  5124-30-1 Vestanat(Evonik) Desmodur (Covestro) Polyethylene glycol 500 250 17557-23-2diglycidyl ether (500) Polypropylene glycol 600 26142-30-3 diglycidylether (600) Ethylene glycol diglycidyl 174 87   224-15-9 ether Propyleneglycol diglycidyl 188 94 16096-30-3 ether Catalysts Dibutyltin dilaurate631.56    77-58-7 (DBTDL) (if using diisocyanates) 2,4,6- 265.39   90-72-2 tris(dimethylaminomethyl)- phenol (DMP-30) (if usingdi-glycidyl ethers) Solvents 1-methoxy-2- 132.2 n/a   108-65-6acetoxypropane Dowanol ™ PMA Glycol Ether Acetate MIBK (4-methyl-2-100.2 n/a   108-10-1 pentanone)Formation of Bis-Thiosemicarbazone of Pyruvaldehyde (2′)

A 250 mL three-necked round-bottom flask was charged with a solution ofthiosemicarbazide (10.02 g, 0.110 mole) dissolved in 100 mL of ethanol.A PTFE stirring bar was added, and the flask was placed in soft heatingmantle on a magnetic stir plate. The center neck was fitted with areflux condenser. One side-neck was fitted with an addition funnelcharged with a solution of pyruvaldehyde dimethyl acetal (5.78 g, 0.049mol) in 50 mL of ethanol. This compound was also called methylglyoxaldimethyl acetal. The other side neck was fitted with a second additionfunnel charged with a solution of 1 mL of 12 N HCl (concentrated HCl) in20 mL of ethanol.

TABLE 2 Mol. Material Wt. Moles Grams mL CASRN Pyruvaldehyde 118.130.049 5.78 5.9 6342-56-9 dimethyl acetal Thiosemi- 91.13 0.11 10.02 n/a  79-19-6 carbazide Ethanol n/a n/a 170 Conc. HCl 12N 0.012 1

The solution of thiosemicarbazide was heated to 50-60 C (just belowreflux). To this was added the solution of pyruvaldehyde dimethyl acetalwith stirring at room temperature over a period of 30-40 minutesfollowed by the solution of HCl. After the acid was added, the heatingmantle and stirrer were turned off, and the mixture was allowed to coolslowly back to room temperature for about two hours. If possible, placethe reaction mixture in a refrigerator for two or three days in increasethe crude yield. The product should precipitate as a yellow solid. Thesolid was collected on a Buchner funnel.

The crude product was recrystallized by dissolving it in the minimumamount of refluxing methanol in a beaker on a hot plate in the fumehood. An equal amount of distilled water was added, removed from heat,and then allowed to cool. Product precipitated as white-yellowishneedles.

Collect by filtration on a Buchner funnel. Dry in oven at 100° F.overnight.

C₅H₁₀N₆S₂: mol. wt. 218.29 Th. Yield=10.69 of product

By-products are 1.09 g of excess thiosemicarbazide, 3.13 g of methanoland 0.88 g of water.

Reference: Petering, 1964.

Reaction of (2) with a Generic Di-Glycidyl Ether

Shown below is the reaction of two Schiff bases (SB) and threediglycidyl ethers. The starting SB is a crystalline solid while theproduct is expected to be a viscous liquid which is more suitable foruse in coating metals surfaces either independently or as an ingredientin a coating formulation. Other difunctional chain extenders could beconsidered.

Schiff Base Oligomer and Epoxy Composition #1

A 500 cc. reaction vessel, fitted with a stirrer and water-cooledcondenser, was charged with 179 grams (0.5 mole) of a diglycidylpolyether of polypropylene glycol having an epoxy equivalent weight of78.5 grams a Schiff base polymer, and 2.6 grams of powdered sodiumhydroxide, as a catalyst. During the first hour, cooling was used tomoderate the reaction at 100° C. to 120 TC. At the end of this hour,less than 1 percent of the diepoxide remained unreacted.

Schiff Base Oligomer and Epoxy Composition #2

2.47 grams of a Schiff base oligomer and epoxy composition or a Schiffbase oligomer composition were mixed with 0.87 gram (0.01 equivalent) oftoluene diisocyanate (TDI) and 1.5 grams dimethylformamide diluent.These compounds were mixed, adding the TDI last. A film was cast on abondarized steel panel and baked for minutes at 300° F. to give athermosetting, clear, orange coating, with a high hardness.

Materials

The table below list materials used as disclosed herein includingexample difunctional chain extending molecules including diglycidylether and diisocyanates.

TABLE 3 Formula CASRN Supplier Quantity Type Aldehydes and thiosemi-carbazide Methyl- CH₃COCH 6342- Sigma 100 mL Keto- glyoxal 1,1- (OCH₃)₂56-9 Aldrich aldehyde didimethyl acetal Acetyl- C₅H₈O₂ 123- Sigma 1 kgdi- acetone (2,4- 54-6 Aldrich ketone pentanedione) Acetonyl- C₆H₁₀O₂110- Sigma 100 mL di- acetone (2,5- 13-4 Aldrich ketone hexanedione)Isophthal- C₈H₆O₂ 626- Sigma 10 g di- aldehyde 19-7 Aldrich aldehydeTerephthal- C₈H₆O₂ 623- Sigma 100 g di- aldehyde 27-8 Aldrich aldehyde5-(hydroxy- C₆H₆O₃ 67- Fisher Aldehyde methyl)- 47-0 Science w/OHfuran-2- carbaldehyde Thiosemi- CH₅N₃S 79- Fisher Thio- carbazide 19-6Science semi- Diglycidyl carbazide ether Poly- 17557- Nagase 20 kgDi-epoxy ethylene 23-2 America glycol diglycidyl ether Ethylene C₈H₁₄O₄2224- Fisher 25 g Di-epoxy glycol 15-9 Science diglycidyl etherSchiff Base Oligomers Having Silyl-End Cap

A solution of 5 grams of the bis-thiosemicarbazone made in the previoussection and 0.05 gram of the appropriate catalyst was dissolved in 25 mLof the desired solvent. This solution was charged to a 100 mLthree-necked round bottom flask containing a PTFE stir bar and fittedwith a reflux condenser, addition funnel, and thermocouple. The flaskwas placed in a water bath, and placed on a magnetic heated stirringplate. The addition funnel was charged with a solution of 1.2equivalents of the desired chain extender dissolved in 25 mL of the samesolvent. This was added dropwise to the flask with stirring over aperiod of 30 minutes, and the temperature was monitored. The temperatureshould rise as the two components combine. The temperature was keptbelow 100 C by appropriate means such as adding ice to the water bath.After one hour, all of the reactive chain extender should be consumed.Residual epoxy content can be determined by a titration (ASTM D1652),and residual isocyanate can be determined by titration (Dow, 2000).

Use of a small amount of trimethoxysilylpropyl glycidyl ether gave anend-group that could react with metal surfaces through metal-O—Si bondformation.

This kind of structure has multiple modes of bonding to a metal surfaceincluding three bis-Schiff base groups, secondary hydroxyl groups, andby, for example, cleavage of the three ethoxysilyl groups with OH groupson the metal surface.

This Schiff base oligomer having a silyl-end cap can be dissolved in anappropriate solution at low solids contents to prepare a solution fordip-coating or spray coating a metal part. Drying could be achieved byheating with IR heat sources, hot air sources, or some combination ofthe two.

Chemical Terms

As used herein, a wavy line of a chemical structure indicates aconnection point between the moiety shown to the rest of the molecule.

The term “composition” as used herein can include the components (e.g.,an oligomer and metal and/or metal salt) and/or reaction product(s) oftwo or more components of the composition.

Unless otherwise stated/claimed, groups/moieties of Schiff baseoligomers described in the present disclosure are unsubstituted orsubstituted. The term “substituted” means that a group is substituted atany available position. Substitution can be with one or more groupsselected from, e.g., alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl,aryl, heterocyclyl, heteroaryl, formyl, alkanoyl, cycloalkanoyl, aroyl,heteroaroyl, carboxyl, alkoxycarbonyl, cycloalkyloxycarbonyl,aryloxycarbonyl, heterocyclyloxycarbonyl, heteroaryloxycarbonyl,alkylaminocarbonyl, cycloalkylaminocarbonyl, arylaminocarbonyl,heterocyclylaminocarbonyl, heteroarylaminocarbonyl, cyano, alkoxy,cycloalkoxy, aryloxy, heterocyclyloxy, heteroaryloxy, alkanoate,cycloalkanoate, aryloate, heterocyclyloate, heteroaryloate,alkylcarbonylamino, cycloalkylcarbonylamino, arylcarbonylamino,heterocyclylcarbonylamino, heteroarylcarbonylamino, nitro, hydroxyl,halo (—F, —Cl, —Br, —I), haloalkyl, haloaryl, haloheterocyclyl,haloheteroaryl, haloalkoxy, silylalkyl, alkenylsilylalkyl,alkynylsilylalkyl, or amino. In some aspects, a substitution may behalo, alkyl, formyl, or amino. The optional substituents may includesalts of the groups, for example carboxylate salts. It will beappreciated that “substituted” may include other groups not specificallydescribed.

“Alkyl” whether used alone, or in compound words such as alkoxy,alkylthio, alkylamino, dialkylamino or haloalkyl, represents straight orbranched chain hydrocarbons ranging in size from one to about 10 carbonatoms, or more. Thus alkyl moieties include, unless explicitly limitedto smaller groups, moieties ranging in size, for example, from one toabout 6 carbon atoms or greater, such as, methyl, ethyl, n-propyl,iso-propyl, butyl, pentyl, hexyl, and higher isomers, including, e.g.,those straight or branched chain hydrocarbons ranging in size from about6 to about 10 carbon atoms, or greater.

“Cycloalkyl” represents a mono- or polycarbocyclic ring system ofvarying sizes, e.g., from about 3 to about 10 carbon atoms, e.g.,cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl. Theterm cycloalkyloxy represents the same groups linked through an oxygenatom such as cyclopentyloxy and cyclohexyloxy. The term cycloalkylthiorepresents the same groups linked through a sulfur atom such ascyclopentylthio and cyclohexylthio.

As will be understood, an aromatic group means a cyclic group having 4m+2 π electrons, where m is an integer equal to or greater than 1. Asused herein, “aromatic” is used interchangeably with “aryl” to refer toan aromatic group, regardless of the valency of aromatic group. Thus,aryl refers to monovalent aromatic groups, bivalent aromatic groups andhigher multivalency aromatic groups.

“Aryl” whether used alone, or in compound words such as arylalkyl,aryloxy or arylthio, represents: (i) an optionally substituted mono- orpolycyclic aromatic carbocyclic moiety, e.g., of about 6 to about 60carbon atoms, such as phenyl, naphthyl or fluorenyl; or, (ii) anoptionally substituted partially saturated polycyclic carbocyclicaromatic ring system in which an aryl and a cycloalkyl or cycloalkenylgroup are fused together to form a cyclic structure such as atetrahydronaphthyl, indenyl, indanyl or fluorene ring.

“Heterocyclyl” or “heterocyclic” whether used alone, or in compoundwords such as heterocyclyloxy represents: (i) an optionally substitutedcycloalkyl or cycloalkenyl group, e.g., of about 3 to about 60 ringmembers, which may contain one or more heteroatoms such as nitrogen,oxygen, or sulfur (examples include pyrrolidinyl, morpholino,thiomorpholino, or fully or partially hydrogenated thienyl, furyl,pyrrolyl, thiazolyl, oxazolyl, oxazinyl, thiazinyl, pyridyl andazepinyl); (ii) an optionally substituted partially saturated polycyclicring system in which an aryl (or heteroaryl) ring and a heterocyclicgroup are fused together to form a cyclic structure (examples includechromanyl, dihydrobenzofuryl and indolinyl); or (iii) an optionallysubstituted fully or partially saturated polycyclic fused ring systemthat has one or more bridges (examples include quinuclidinyl anddihydro-1,4-epoxynaphthyl).

A heteroaromatic group is an aromatic group or ring containing one ormore heteroatoms, such as N, O, S, Se, Si or P. As used herein,“heteroaromatic” is used interchangeably with “heteroaryl”, and aheteroaryl group refers to monovalent aromatic groups, bivalent aromaticgroups and higher multivalency aromatic groups containing one or moreheteroatoms. “Heteroaryl” is considered one non-limiting type of“heterocyclyl”.

“Heteroaryl”, whether used alone, or in compound words such asheteroaryloxy represents: (i) an optionally substituted mono- orpolycyclic aromatic organic moiety, e.g., of about 1 to about 10 ringmembers in which one or more of the ring members is/are element(s) otherthan carbon, for example nitrogen, oxygen, sulfur or silicon; theheteroatom(s) interrupting a carbocyclic ring structure and having asufficient number of delocalized pi electrons to provide aromaticcharacter, provided that the rings do not contain adjacent oxygen and/orsulfur atoms. Typical 6-membered heteroaryl groups are pyrazinyl,pyridazinyl, pyrazolyl, pyridyl and pyrimidinyl. All regioisomers arecontemplated, e.g., 2-pyridyl, 3-pyridyl and 4-pyridyl. Typical5-membered heteroaryl rings are furyl, imidazolyl, oxazolyl, isoxazolyl,isothiazolyl, oxadiazolyl, pyrrolyl, 1,3,4-thiadiazolyl, thiazolyl,thienyl, triazolyl, and silole. All regioisomers are contemplated, e.g.,2-thienyl and 3-thienyl. Bicyclic groups typically are benzo-fused ringsystems derived from the heteroaryl groups named above, e.g.,benzofuryl, benzimidazolyl, benzthiazolyl, indolyl, indolizinyl,isoquinolyl, quinazolinyl, quinolyl and benzothienyl; or, (ii) anoptionally substituted partially saturated polycyclic heteroaryl ringsystem in which a heteroaryl and a cycloalkyl or cycloalkenyl group arefused together to form a cyclic structure such as a tetrahydroquinolylor pyrindinyl ring.

“Hydroxyl” and “hydroxy” can be used interchangeably and represent a —OHmoiety.

“Alkoxy” and “alkoxyl” can be used interchangeably and represent an—O-alkyl group in which the alkyl group is as defined supra. Examplesinclude methoxy, ethoxy, n-propoxy, iso-propoxy, and the differentbutoxy, pentoxy, hexyloxy and higher isomers.

“Aryloxy” and “aryloxyl” can be used interchangeably and represent an—O-aryl group in which the aryl group is as defined supra. Examplesinclude, without limitation, phenoxy and naphthoxy.

The compounds described herein may include salts, solvates, hydrates,isomers, tautomers, racemates, stereoisomers, enantiomers ordiastereoisomers of those compounds. For example, salts may includesodium, potassium, calcium, nitrates, phosphates, sulfates, chlorides,or combinations thereof.

While the foregoing is directed to aspects of the present disclosure,other and further aspects of the disclosure may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. An oligomer represented by Formula (IV):

wherein: each instance of R⁹ is independently selected from the groupconsisting of alkyl, cycloalkyl, aryl, heteroaryl, and ether; eachinstance of R²⁸ and R²⁹ is independently selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, and aryl; each instance ofR³³ is independently selected from the group consisting of alkyl,cycloalkyl, aryl, heterocyclyl, and a bond; each instance of R⁴¹ isindependently —NH— or a bond and each instance of R⁴⁰ is independently—NH— or —NH—NH—; each instance of R⁴² is independently —NH— or a bondand each instance of R⁴³ is independently —NH— or —NH—NH—; each instanceof z and t is an integer of 1 to 50; R⁴⁴ is hydroxyl or decarboxylatedderivative thereof, or is represented by the structure:

wherein: R¹ is hydrogen or silyl; R² and R³ are independently selectedfrom the group consisting of hydrogen, alkyl, cycloalkyl, and aryl; R³¹is selected from the group consisting of alkyl, cycloalkyl, aryl,heterocyclyl, and a bond; R⁵⁰ is —NH— or a bond and R³² is —NH— or—NH—NH—; R³⁴ is —NH— or a bond and R³⁵ is —NH— or —NH—NH—; and x is aninteger of 1 to 50; and R³⁰ is hydrogen, silyl, or is represented by thestructure:

where: R^(9′) selected from the group consisting of alkyl, cycloalkyl,aryl, heteroaryl, and ether; and R^(44′) is hydroxyl or decarboxylatedderivative thereof.
 2. The oligomer of claim 1, wherein each instance ofR²⁸ or R²⁹ is independently selected from the group consisting ofhydrogen and C₁-C₈ alkyl.
 3. The oligomer of claim 2, wherein eachinstance of R²⁸ or R²⁹ is hydrogen.
 4. The oligomer of claim 1, wherein:if R⁴¹ is —NH—, then R⁴⁰ is —NH—, and if R⁴¹ is a bond, then R⁴⁰ is—NH—NH—; and if R⁴² is —NH—, then R⁴³ is —NH—, and if R⁴² is a bond,then R⁴³ is —NH—NH—.
 5. The oligomer of claim 1, wherein each instanceof R⁹ is independently C₁-C₁₀ alkyl or an aryl.
 6. The oligomer of claim1, wherein each instance of R⁹ is independently a phenyl represented bythe formula:

wherein R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from the groupconsisting of hydrogen, and C₁-C₁₀ alkyl.
 7. The oligomer of claim 6,wherein each of R⁶⁰, R⁶¹, R⁶², and R⁶³ is hydrogen.
 8. The oligomer ofclaim 1, wherein each instance of R⁹ is cycloalkyl.
 9. The oligomer ofclaim 1, wherein each instance of R³³ is a bond.
 10. The oligomer ofclaim 1, wherein each instance of R³³ is independently selected fromC₁-C₁₀ alkyl.
 11. The oligomer of claim 1, wherein each instance of R³³is independently selected from a phenyl represented by the formula:

where R⁶⁰, R⁶¹, R⁶², and R⁶³ are independently selected from hydrogenand C₁-C₁₀ alkyl.
 12. The oligomer of claim 11, wherein each of R⁶⁰,R⁶¹, R⁶², and R⁶³ is hydrogen.
 13. The oligomer of claim 1, wherein R³⁰is hydrogen.
 14. The oligomer of claim 1, wherein R⁴⁴ is hydroxyl. 15.The oligomer of claim 1, wherein R³⁰ is silyl.
 16. The oligomer of claim15, wherein the silyl derived from is a glycidyl ether silyl.
 17. Theoligomer of claim 15, wherein the silyl is represented by the formula:

wherein each of R⁴⁵, R⁴⁶, and R⁴⁷ is independently selected from thegroup consisting of hydrogen and C₁-C₂₀ alkyl; and R⁴⁸ is selected fromthe group consisting of alkyl, cycloalkyl, ether, and aryl.
 18. Theoligomer of claim 17, wherein each of R⁴⁵, R⁴⁶, and R⁴⁷ is hydrogen. 19.The oligomer of claim 17, wherein each of R⁴⁵, R⁴⁶, and R⁴⁷ is ethyl.20. The oligomer of claim 17, wherein R⁴⁸ is ether.